The present invention relates to a blade attaching and detaching mechanism for saber saws. Various saber saws have been conventionally developed to cut or saw woody or steel materials or pipes in the housing or building construction sites or similar fields.
The saber saw is a cutting tool with a reciprocating plunger driven by an electric motor. A blade has an engaging hole engageable with the plunger.
The normal size plungers have a reciprocating stroke of approximately 20 mm to 32 mm. In actual cutting or sawing operations, the blade is locally worn at the limited region corresponding to the reciprocating stroke. Especially, blades are frequently broken during the cutting operation of a steel member. A long blade tends to be broken at its proximal end closer to the plunger. In many cases, the blades are broken and the user is forced to exchange the blades frequently.
To exchange the blades, using a wrench or a specialized tool is popular. However, using the wrench or specialized tool is inefficient because it takes a long time to complete the attaching or detaching operation. Moreover, the user may lose the wrench or specialized tool.
U.S. Pat. Nos. 5,443,276; 5,575,071; 5,647,133; and 4,299,402 disclose toolless blade attaching and detaching mechanisms capable of exchanging the blades without using a wrench or similar tool.
For example, U.S. Pat. Nos. 5,443,276; 5,575,071; and 5,647,133 disclose the toolless blade attaching and detaching mechanisms having a steel ball or a movable locking pin which is engageable with a hole of the blade. A lever or a rotary ring is provided to hold the attached blade or to disengage the steel ball or the movable locking pin from the blade.
However, these conventional toolless blade attaching and detaching mechanisms basically force the use to touch the blade for removing the blade or its broken piece. During the removing operation, the sharp edge of the blade may injure the user's hand. The blade surface has a high temperature due to friction during the cutting or sawing operation. The user's hand may be burned by the heated blade surface.
When the blade is broken at the proximal end, a small piece of the blade will be left in a narrow space of the plunger. It takes a long time to completely remove such a small piece remaining in the narrow space of the plunger.
According to the toolless blade attaching and detaching mechanisms disclosed in U.S. Pat. Nos. 5,443,276 and 5,575,071, the user is required to hold the lever or the rotary ring at a predetermined unlock position of the locking pin against the resilient force during the blade attaching and detaching operation. In other words, the user must use both hands simultaneously.
Furthermore, the blade has an elongated shape and therefore easily causes a lateral vibration when it reciprocates at a high speed.
The toolless blade attaching and detaching mechanisms disclosed in U.S. Pat. Nos. 5,443,276 and 5,647,133 comprise complicated parts exposed outside the saber saw. This is disadvantageous in that such complicated parts may be damaged by a cut or sawed member during the cutting or sawing operation.
Furthermore, according to the toolless blade attaching and detaching mechanism disclosed in U.S. Pat. No. 4,299,402, it is difficult to press a side surface of the blade. The blade will be subjected to a severe vibration.